html{
    height: 100%;
}
body{
    margin: 0px;
    height: 100%;
    color: white;
}
main{
    /*设置main为弹性盒子，让它内部的子元素做弹性布局*/
    display: flex;
    /*调整主轴方向*/
    flex-direction: column;
    /*设置主轴与交叉轴方向的对齐方式*/
    justify-content: space-around;
    align-items: center;

    height: 100%;
    width: 100%;

    position: absolute;
    top: 0px;
    left: 0px;
    z-index: 1;
    
}

/*1.头部的三个按钮*/
#btns{
    width: 100%;
    display: flex;
    justify-content: space-between;
}
#btns input{
    border: none;
    /*rgb: red/green/blue 三原色，取值范围：0~255；
    a:alpha, 透明度 取值范围：0~1*/
    background-color: rgba(0, 0, 0, 0);
    font-size: 0.9rem;
    color: white;
}
#btns input:nth-child(2){
    font-size: 1rem;
}

/*2.头像*/
#photo img{
    width: 6rem;
    border-radius: 50%;
}

/*3.账号密码*/
form #account{
    margin-bottom: 15px;
}
form div{
    border-bottom: 1px solid gray;
    padding-bottom: 3px;
}
form input{
    border: none;
    background-color: rgba(0, 0, 0, 0);
    color: white;
    font-size: 1rem;
}
form label{
    padding: 1px;
    margin-right: 1rem;
}

/*4.登陆、忘记密码*/
#login a{
    display: block;
    text-align: center;
    margin-top: 10px;

    color: gray;
    font-size: 0.8rem;
    text-decoration: none;
}
#login button{
    width: 7rem;
    height: 2rem;
    border: none;
    background-color: green;
    color: white;
    border-radius: 5px;
}

/*5.其他登陆方式*/
footer{
    width: 80%;
    display: flex;
    justify-content: space-around;
}
footer img{
    width: 3.5rem;
}

/*模糊背景*/
#bg{
    width: 100%;
    height: 100%;

    background-image: url(bg.jpg);
    background-repeat: no-repeat;
    background-size: auto 100%;
    background-position: center center;
    /*滤镜，blur（）实现模糊效果，值越大越模糊*/
    filter: blur(10px);
    position: absolute;
    top: 0px;
    left: 0px;
}